OP-1 Compared with Iliac Crest Autograft in Instrumented Posterolateral Fusion: A Randomized, Multicenter Non-Inferiority Trial.

BACKGROUND: Spinal fusion with the use of autograft is a commonly performed procedure. However, harvesting of bone from the iliac crest is associated with complications. Bone morphogenetic proteins (BMPs) are extensively used as alternatives, often without sufficient evidence of safety and efficacy. The purpose of this study was to investigate non-inferiority of osteogenic protein-1 (OP-1, also known as BMP-7) in comparison with iliac crest bone graft in posterolateral fusions. METHODS: This study was a randomized, controlled multicenter trial. Patients who underwent a single-level instrumented posterolateral fusion of the lumbar spine for degenerative or isthmic spondylolisthesis with symptoms of neurological compression were randomized to receive OP-1 combined with local bone (OP-1 group) or autologous bone graft from the iliac crest combined with local bone (autograft group). The primary outcome was overall success, defined as a combination of clinical success and evidence of fusion on computed tomography (CT) scans, at one year postoperatively. RESULTS: One hundred and nineteen patients were included in the study, and analysis of the overall outcome was performed for 113. Non-inferiority of OP-1 compared with iliac crest autograft was not found at one year, with a success rate of 40% in the OP-1 group versus 54% in the autograft group (risk difference = -13.3%, 90% confidence interval [CI] = -28.6% to +2.10%). This was due to the lower rate of fusion (the primary aim of OP-1 application) seen on the CT scans in the OP-1 group (54% versus 74% in the autograft group, p = 0.03). There were no adverse events that could be directly related to the use of OP-1. CONCLUSIONS: OP-1 with a collagen carrier was not as effective as autologous iliac crest bone for achieving fusion and cannot be recommended in instrumented posterolateral lumbar fusion procedures. LEVEL OF EVIDENCE: Therapeutic Level I. See Instructions for Authors for a complete description of levels of evidence.

No correlation between slip reduction in low-grade spondylolisthesis or change in neuroforaminal morphology and clinical outcome.

BACKGROUND: In instrumented posterolateral fusion reduction of a spondylolisthesis is appealing on theoretical grounds since this may lead to indirect decompression of the entrapped nerve roots. However, there is no consensus in the literature whether a beneficial effect of reduction on outcome can be expected. The objective of the current study was to evaluate whether a correlation between the extent of listhesis reduction and clinical improvement could be established. METHODS: From two ongoing prospective studies 72 patients with a single-level instrumented posterolateral lumbar fusion for low-grade spondylolisthesis (isthmic/degenerative 51/21) were evaluated. Radiographs and clinical outcome scores were available at baseline, 6 weeks and 1 year after surgery. Changes in neuroforaminal morphology were measured on calibrated radiographs. These changes in radiographic parameters were correlated to clinical outcome (Visual Analogue Score (VAS) leg pain, Oswestry Disability Index (ODI)). Fusion status was assessed on Computed Tomography-scan at one year. RESULTS: A mean spondylolisthesis of 25 percent was reduced to 15 percent at 6 weeks with some loss of reduction to 17 percent at one year. The VAS and ODI significantly improved at both time intervals after surgery (p < 0.001). No significant correlations could be established between the extent of slip reduction and improvement in VAS or ODI (Pearson's correlation -0.2 and 0.07 respectively at one year); this also accounted for the other radiographic parameters. A fusion rate of 64 percent was seen on CT-scan. CONCLUSIONS: Clinical outcome was not related to the obtained radiographic reduction of the slipped vertebra in patients with a lumbar fusion for low grade spondylolisthesis. Loss of reduction or non-union on CT-scans had no effect on the clinical outcome. Reduction of a low-grade spondylolisthesis in spinal fusion is appealing, however, there is no evidence that it positively affects clinical outcome on the short term. TRIAL REGISTRATION: ISRCTN43648350.